<html><!-- Created using the cpp_pretty_printer from the dlib C++ library.  See http://dlib.net for updates. --><head><title>dlib C++ Library - general_hash.h</title></head><body bgcolor='white'><pre>
<font color='#009900'>// Copyright (C) 2003  Davis E. King (davis@dlib.net)
</font><font color='#009900'>// License: Boost Software License   See LICENSE.txt for the full license.
</font><font color='#0000FF'>#ifndef</font> DLIB_GENERAL_HASh_
<font color='#0000FF'>#define</font> DLIB_GENERAL_HASh_


<font color='#0000FF'>#include</font> <font color='#5555FF'>&lt;</font>string<font color='#5555FF'>&gt;</font>
<font color='#0000FF'>#include</font> "<a style='text-decoration:none' href='hash.h.html'>hash.h</a>"

<font color='#0000FF'>namespace</font> dlib 
<b>{</b>

<font color='#009900'>// ----------------------------------------------------------------------------------------
</font><font color='#009900'>// ----------------------------------------------------------------------------------------
</font><font color='#009900'>// ----------------------- provide a general hashing function object ----------------------
</font><font color='#009900'>// ----------------------------------------------------------------------------------------
</font><font color='#009900'>// ----------------------------------------------------------------------------------------
</font>
    <font color='#0000FF'>template</font> <font color='#5555FF'>&lt;</font>
        <font color='#0000FF'>typename</font> T
        <font color='#5555FF'>&gt;</font>
    <font color='#0000FF'>class</font> <b><a name='general_hash'></a>general_hash</b>
    <b>{</b>
    <font color='#0000FF'>public</font>:
        <font color='#0000FF'>inline</font> <font color='#0000FF'><u>unsigned</u></font> <font color='#0000FF'><u>long</u></font> <b><a name='operator'></a>operator</b><font face='Lucida Console'>(</font><font face='Lucida Console'>)</font> <font face='Lucida Console'>(</font>
            <font color='#0000FF'>const</font> T<font color='#5555FF'>&amp;</font> item
        <font face='Lucida Console'>)</font> <font color='#0000FF'>const</font>;
    <b>}</b>;
    <font color='#009900'>/*!
        Note that the default behavior of general hash is to attempt to cast
        an object of type T to an unsigned long and use that as the hash.

        REQUIREMENTS ON general_hash
            - must have a default constructor
            - must be a function object which overloads operator() as follows:
              unsigned long operator()(const T&amp; item)             
            - must take item, compute a hash number and return it 
            - must not throw
            - must define the hash in such a way that all equivalent objects have 
              the same hash.  where equivalent means the following:
                  definition of equivalent:
                  a is equivalent to b if
                  a &lt; b == false and
                  b &lt; a == false
    !*/</font>

<font color='#009900'>// ---------------
</font>
    <font color='#0000FF'>template</font> <font color='#5555FF'>&lt;</font>
        <font color='#0000FF'>typename</font> T
        <font color='#5555FF'>&gt;</font>
    <font color='#0000FF'><u>unsigned</u></font> <font color='#0000FF'><u>long</u></font> general_hash<font color='#5555FF'>&lt;</font>T<font color='#5555FF'>&gt;</font>:: 
    <b><a name='operator'></a>operator</b><font face='Lucida Console'>(</font><font face='Lucida Console'>)</font> <font face='Lucida Console'>(</font>
        <font color='#0000FF'>const</font> T<font color='#5555FF'>&amp;</font> item
    <font face='Lucida Console'>)</font> <font color='#0000FF'>const</font>
    <b>{</b>
        <font color='#009900'>// hash any types that have a conversion to uint64 
</font>        <font color='#0000FF'>return</font> <font color='#BB00BB'>hash</font><font face='Lucida Console'>(</font><font color='#0000FF'>static_cast</font><font color='#5555FF'>&lt;</font>uint64<font color='#5555FF'>&gt;</font><font face='Lucida Console'>(</font>item<font face='Lucida Console'>)</font><font face='Lucida Console'>)</font>;
    <b>}</b>


<font color='#009900'>// ---------------
</font>
    <font color='#009900'>// std::string hash
</font>    <font color='#0000FF'>template</font> <font color='#5555FF'>&lt;</font><font color='#5555FF'>&gt;</font>
    <font color='#0000FF'>inline</font> <font color='#0000FF'><u>unsigned</u></font> <font color='#0000FF'><u>long</u></font> general_hash<font color='#5555FF'>&lt;</font>std::string<font color='#5555FF'>&gt;</font>:: 
    <b><a name='operator'></a>operator</b><font face='Lucida Console'>(</font><font face='Lucida Console'>)</font> <font face='Lucida Console'>(</font>
        <font color='#0000FF'>const</font> std::string<font color='#5555FF'>&amp;</font> item
    <font face='Lucida Console'>)</font> <font color='#0000FF'>const</font>
    <b>{</b>
        <font color='#0000FF'>return</font> <font color='#BB00BB'>hash</font><font face='Lucida Console'>(</font>item<font face='Lucida Console'>)</font>;
    <b>}</b>

<font color='#009900'>// ----------------------------------------------------------------------------------------
</font><font color='#009900'>// ----------------------------------------------------------------------------------------
</font>
<b>}</b>

<font color='#0000FF'>#endif</font> <font color='#009900'>// DLIB_GENERAL_HASh_
</font>

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